Yup, if you shoot balls, use 457 dia. They shave a nice ring when rammed into chambers. That shows a good seal. You can add some lube to the top of the ball after loading too if needed.
I have a pair of 5 1/2" stainless ROAs that I installed Kirst Converters in. I load my own ammo and shoot BP in al my cartridges. I use a 454 dia bullet. I currently shoot a special one that I cast myself called a PRS. It has a huge lube capacity.
I am getting quite a collection going of ROAs. I have 6 of them now. I just got a new pair of blue 7 1/2s with fixed sights.
Yup, they are heavy, especially when loaded, but that heft seems to tame recoil very well. I can shoot them all day one handed with stiff loads and not feel strained or tired. What I am trying to say I love them :wink:
Good luck with yours.